A substrate, at least one surface of which is partially or entirely flat, the substrate having: a substrate molded from first substrate-forming particles; second substrate-forming particles partially or entirely filled into first pores which are formed by the first substrate-forming particles on at least one surface of the substrate; and a polymer partially or entirely filled into second pores remaining in a region in which the second substrate-forming particles are filled. Also disclosed is a method for preparing a thin or thick film, including the aligning non-spherical seed crystals on a flat portion of at least one surface of the substrate such that an a-axis, a b-axis, and/or a c-axis are oriented according to a certain rule; and exposing the aligned seed crystals to a solution for enabling the growth of the seed crystals to thereby form and grow a film from the seed crystals using a secondary growing technique.